Fiber optics switches are usually characterized with respect to their losses (insertion, transmission and reflection), switching time, repeatability, long term stability, temperature and vibration resistance, power handling, wavelength-range and number of ports. Various architectures and concepts have been proposed for optical routing with fiber optical switches among them systems based on movement (e.g. physical translation and bending) of fibers by directly moving the fiber, by moving the position of a reflective or refractive object, by altering the polarization in birefringent systems and through interferences caused by changes in the phase (spatial or temporal) of the optical signal.
Fiber optical systems involving physical effects such as polarization, birefringence, refraction and interference are sensitive to the optical wavelength and therefore manifest significant limitations in broadband optical signal switching applications. In particular for applications where the optical wavelength lies beyond the near infrared optical spectrum, including the mid-wave and long-wave infrared, many of the optical elements required for the polarization and interference switches have limited applicability or are not available. Fiber optical systems based on the movement of fiber for direct end-to-end fiber coupling or imaging-type systems including reflective mirror-type approaches are not as sensitive to the wavelength of light providing a viable alternative for broadband applications.
For switch alternatives based-on imaging-type and reflective mirror-type fiber optical systems, the optical signal has to exit the fiber and interact with at least another optical element reaching the routing fiber. Optical power handling in these systems is limited by the optical coating and the size of the optical elements used. Typically, the increase in the size of the optics correlates with increased switching times as more mass or larger distances need to be moved. Systems based on the movement of fibers such as end-to-end fiber coupling are power limited only by the maximum power handling of the optical fiber transmitting the signal.
US Patent Application No. 20040057654 to Baasch, describes a method for optical switching based on magnetic-actuation of an optical fiber. The optical fiber has a small magnetic bead attached to the end of the fiber, upon action of a magnetic field the bead (and hence the fiber) is attracted towards the magnet. Two fibers are placed along a horizontal plane defined by the magnets, allowing the signal to be switched from one fiber to another. U.S. Pat. No. 4,652,081 to Fatatry, describes a method for electro-magnetically translating a fiber among multiple fibers into a funnel shaped guide thereby aligning the selected fiber with the input fiber inside the guide. Neither of these approaches provides both simple fiber movements systems while providing the user with the flexibility of connecting the switch with other than a fixed number of ports.
It is therefore desirable to provide an optical fiber switch capable for use with simple fiber movements systems while also providing the design flexibility for use in different applications requiring disparate numbers of ports.